Wednesday, October 25, 2017

Earthquake Warnings Could Come One Week in Advance Thanks to Rock Sounds

Tiny sounds from rocks might help tip off scientists to earthquakes one week in advance.
A recent paper in the Geophysical Research Letters journal outlines what could be the most advanced method yet for detecting earthquakes well ahead of time—giving people days, rather than moments, to find safety.
The paper describes a computer program that eavesdrops on quiet rumbles made by rocks deep inside the Earth. Scientists have long known about these sounds but until now haven’t found a deeper pattern in them.
"What happens before an earthquake is that rocks emit noise because one grain of rock is rubbing against another grain of rock," co-author Colin Humphreys, a materials scientist at Cambridge University, told Reuters. "It’s a little like a squeaky door."
There's always a little rumbling in the Earth, but the team found they could train a computer to recognize changes in that rumbling that occur when an earthquake is imminent—about a week away, according to Humphrey.
Despite the paper’s proposal, week-long earthquake warnings won't become a standard practice any time soon. The new study only looked at laboratory-generated seismic activity, not natural earthquakes, which means the team wants to test the same approach on a real fault like California's infamous San Andreas fault.
10_24_mexico_earthquake_warning The September earthquake damaged buildings across central Mexico. Hector Vivas/Getty Images
Current earthquake warning systems—such as Mexico City's, which was able to give residents 20 seconds of warnings before last month's giant quake—rely on catching earthquakes at their source. Then, it's a simple race: An earthquake's waves of energy travel through solid rock (75 miles's worth, in Mexico City’s case) slower than radio waves travel through air. That discrepancy means a radio warning can edge out in front of the actual earthquake.
10_24_mexico earthquake_car This car was destroyed when a building collapsed during the earthquake that struck Mexico in September. Hector Vivas/Getty Images
That's the same sort of system that the U.S. Geological Survey is developing for the West Coast, where the government estimates California is nearly certain to be hit within the next three decades by a quake with a magnitude of at least 6.7. (The recent Mexico earthquake was magnitude 8.2.) Even a minute or two can be enough time to evacuate unsafe buildings, clear off bridges, and otherwise reduce immediate injuries and deaths.
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